Prior to the present invention, various techniques were developed for eliminating PCBs, or polychlorinated biphenyls from the environment. In instances where the PCBs were dissolved in an organic solvent, such as transformer oil, the contaminated solution could be treated with a mixture of polyethylene glycol and alkali metal hydroxide as shown by Brunelle, U.S. Pat. No. 4,351,718, assigned to the same assignee as the present invention and incorporated herein by reference. In many cases, the PCBs are located in more exposed environmental areas, such as landfill sites, river beds and sewage sludge. Direct chemical treatment of PCBs in such contaminated sites if often not feasible since the resulting treated solids are difficult to process further and recycle.
As shown by Colaruotolo et al., U.S. Pat. No. 4,477,570, an alternate procedure can be used for treating halogenated organic waste by effecting the removal of halogenated aromatics from the contaminated organic waste by microbial degradation. As taught by Colaruotolo et al., microorganisms have been identified having the capability of efficiently utilizing various aromatic organic chemicals as carbon sources for growth. In addition, microorganisms also have been isolated from the environment that are capable of growing in the presence of chlorinated aromatic compounds. Experience has shown, however, that PCBs found in weathered environmental soil samples, often contain five or more chlorine atoms per molecule, indicating that such polychlorinated biphenyls generally resist biodegradation.
Alternatively, as taught by J. F. Brown et al, Northeastern Environmental Science 3:167-179 (1984), PCBs in anaerobic river and lake sediments contaminated with Aroclor 1242, a PCB mixture identified further hereinafter as containing chlorobiphenyls with 2-5 chlorines per molecule or Aroclor 1254, a PCB mixture containing chlorobiphenyls with 4-7 chlorines per molecule, have undergone extensive dechlorination. The net effect of this dechlorination is the depletion of highly chlorinated biphenyls and an accumulation of mono-, di-, and trichlorobiphenyls containing 1-3 ortho chlorines. Apparently, ortho chlorines are not readily removed by the agent (presumably anaerobic bacteria) which removes meta- and para-chlorines.
The present invention is based on the discovery that certain strains of Alcaligenes eutrophus, identified more particularly hereinafter, have been found effective for aerobic biodegradation of PCBs having several and up to more than five chlorine atoms per molecule. Further, the Alcaligenes eutrophus bacteria used in the practice of the invention has also been found effective for further biodegrading dechlorinated PCBs extracted from river or lake sediment. In addition, in particular instances, metabolite resulting from the biodegradation of the PCB contaminated organic waste, can comprise cis-3,4-dihydro-3,4-dihydroxy chlorobiphenyls, ring chlorinated acetophenones, or derivatives thereof.